Distinctive requirement of PKCε in the control of Rho GTPases in epithelial and mesenchymally transformed lung cancer cells

• Published in: Oncogene Vol. 38; no. 27; pp. 5396 - 5412
• Main Authors: Casado-Medrano, Victoria, Barrio-Real, Laura, Wang, Anita, Cooke, Mariana, Lopez-Haber, Cynthia, Kazanietz, Marcelo G
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 04.07.2019
• Subjects: Carcinoma, Non-Small-Cell Lung - enzymology; Carcinoma, Non-Small-Cell Lung - pathology; Cell Line, Tumor; Cytology; Diglycerides; Diglycerides - metabolism; Down-Regulation - drug effects; Enzyme Activation; Epithelial-Mesenchymal Transition - drug effects; Genotype & phenotype; Guanine; Humans; Isoenzymes; Kinases; Lung cancer; Lung Neoplasms - enzymology; Lung Neoplasms - pathology; Mesenchyme; Metastases; Non-small cell lung carcinoma; Phenotypes; Protein kinase C; Protein Kinase C-epsilon - metabolism; Rac1 protein; rho GTP-Binding Proteins - metabolism; RhoA protein; Transformed cells; Transforming Growth Factor beta - pharmacology; Transforming growth factor-b; Up-Regulation - drug effects
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/s41388-019-0796-4

Diacylglycerol (DAG)/phorbol ester-regulated protein kinase C (PKC) isozymes have been widely linked to tumor promotion and the development of a metastatic phenotype. PKCε, an oncogenic member of the PKC family, is abnormally overexpressed in lung cancer and other cancer types. This kinase plays significant roles in proliferation, survival, and migration; however, its role in epithelial-to-mesenchymal transition (EMT) has been scarcely studied. Silencing experiments in non-small lung cancer (NSCLC) cells revealed that PKCε or other DAG-regulated PKCs (PKCα and PKCδ) were dispensable for the acquisition of a mesenchymal phenotype induced by transforming growth factor beta (TGF-β). Unexpectedly, we found a nearly complete down-regulation of PKCε expression in TGF-β-mesenchymally transformed NSCLC cells. PMA and AJH-836 (a DAG-mimetic that preferentially activates PKCε) promote ruffle formation in NSCLC cells via Rac1, however they fail to induce these morphological changes in TGF-β-mesenchymally transformed cells despite their elevated Rac1 activity. Several Rac guanine nucleotide exchange-factors (Rac-GEFs) were also up-regulated in TGF-β-treated NSCLC cells, including Trio and Tiam2, which were required for cell motility. Lastly, we found that silencing or inhibiting PKCε enhances RhoA activity and stress fiber formation, a phenotype also observed in TGF-β-transformed cells. Our studies established a distinctive involvement of PKCε in epithelial and mesenchymal NSCLC cells, and identified a complex interplay between PKCε and small GTPases that contributes to regulation of NSCLC cell morphology and motile activity.